NFC Ring Lock Box

[Nairod785] wanted to build a lock box that would lock from the inside. He started with an inexpensive, plain wooden box. This kept the cost down but would also allow him to easily decorate the box later on using a wood burning tool.

To keep the box locked, he installed a simple latch on the inside. The latch is connected to a servo with string. When the servo rotates in one direction, it pulls the string and releases the latch. When the servo is rotated in the opposite direction, the latch closes and locks the box once again.

If you are going to have a locked box, then you are also going to need a key to open it. [Nairod785] used a ring with a built-in NFC tag, similar to the ring featured back in March. Inside of the box is a PN532 NFC module. The walls of the box were a little too thick for the reader to detect the ring, so [Nairod785] had to scratch the wall thickness down a bit. The NFC module is connected to an Arduino Nano. Communications are handled with I2C.

The NFC ring actually has two different NFC tags in it; one on each side. [Nairod785] had to program both of the tag ID’s into the Arduino to ensure that the ring would work no matter the orientation.

The system is powered by a small rechargeable 5V battery. [Nairod785] wired up a USB plug flush with the box wall so he can easily charge up the battery while the box is locked. It also allows him to reprogram the Arduino if he feels so inclined. There is also a power switch on the side to conserve energy.

@Longshot
The following is going to assume this is the illegal kind of intrusion, because if you’re just trying to get at daddy’s vintage porn tapes then holy hell are you overthinking this:

Evidence is only material *if it gets you caught*. It will only get you caught if it is found, recognized as evidence, and can be associated with you. Any one of these not happening dead-ends the investigation.

Spending additional time trespassing in someone’s home is dramatically more likely to leave the kind of evidence that gets you caught (or to directly get you caught). This is precisely why burglars tend just dump drawers and sweep stuff off shelves: the number one priority is get in and get out quickly. Far better to grab the box, leave, crack it open in a safe place, leave it in a dumpster in front of someone else’s apartment building (or burn the box and trash the electronic parts), and have a trusted third party pawn the goods, preferably in a different town than the victim.

heh Once I opened a Sparc pizza box and all I had was a crowbar. Man Sun really built those things let me tell you! It looked more like a potato chip by the time I got it open. What I’m saying is some boxes can put up more of a fight than their appearance suggests that they can. I was demolishing the building that computer was in so the crowbar I had was a pretty hefty one. It was going into a dumpster anyways, just like the rest of the place was. We just wanted to see if it had RAM sticks inside of it that we could use. It didn’t. Actually all of the e trash ended up going into 55 gallon drums as toxic waste. Except for a couple of truckloads of it that we took to a computer store down the highway and sold off.